Plasma etching method and plasma etching apparatus

ABSTRACT

There are provided a plasma etching method and a plasma etching apparatus capable of independently controlling distributions of line widths and heights of lines in a surface of a wafer. The plasma etching method for performing a plasma etching on a substrate W by irradiating plasma containing charged particles and neutral particles to the substrate W includes controlling a distribution of reaction amounts between the substrate W and the neutral particles in a surface of the substrate W by adjusting a temperature distribution in the surface of the substrate W supported by a support  105 , and controlling a distribution of irradiation amounts of the charged particles in the surface of the substrate W by adjusting a gap between the substrate W supported by the support  105  and an electrode  120  provided so as to face the support  105.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2010-054828 filed on Mar. 11, 2010, the entire disclosures of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to a plasma etching method and a plasmaetching apparatus for performing a plasma etching on a substrate.

BACKGROUND OF THE INVENTION

In manufacturing a semiconductor device, as an apparatus for processinga substrate such as a semiconductor wafer (hereinafter, referred to as“wafer”), there has been used a plasma etching apparatus which performsan etching process on the wafer by irradiating plasma to the wafer.

By way of example, a wafer yet to be processed in the above-describedplasma etching apparatus is formed of a silicon substrate. On the wafer,a silicon dioxide (SiO₂) film, an etching target film formed of apolysilicon film, a mask film formed of a single layer or multiplelayers, a bottom anti-reflective coating BARC, and a photoresist film(hereinafter, referred to as “resist film”) are formed in sequence fromthe bottom. The resist film is exposed and developed in advance, and apattern having lines is formed on the resist film. By etching the bottomanti-reflective coating, the mask film, the etching target film insequence, the pattern having lines is formed on the etching target film.The above-described example in which the etching target film is formedof a polysilicon film may be related to a gate etching process in whichan etching target film serves as a gate electrode, for example.

However, recently, in manufacturing a semiconductor device, a waferbecomes larger. As the wafer becomes larger, it becomes difficult toobtain uniformity in line widths CD (critical dimension) and a height oflines formed on the surface of the wafer.

In the above-described etching process, a gas including fluorine,chlorine, oxygen or the like is used as a processing gas. When the waferis etched, the fluorine, chlorine, oxygen or the like included in theprocessing gas may be excited into plasma. The plasma includes chargedparticles (hereinafter, referred to as “ions”) and neutral particles(hereinafter, referred to as “radicals”). The surface of the waferreacts with the plasma including the ions and radicals, so that areaction product is generated and the reaction product is volatilized.In this way, the etching process proceeds.

The reaction product generated by the reaction between the surface ofthe wafer and the plasma may adhere to the lines formed on the waferagain. Therefore, the line widths of the lines formed by the etchingprocess may vary depending on a probability that the reaction productmay adhere to the lines again (hereinafter, referred to as “adhesioncoefficient”). Since the adhesion coefficient depends on a temperatureof the wafer, the line widths of the lines formed on the wafer may varydepending on the temperature of the wafer. Accordingly, there has beensuggested a plasma etching apparatus that performs an etching processwith high uniformity in line widths of the lines formed on a wafer bycontrolling a temperature distribution in a surface of the wafer (see,for example, Patent Document 1).

The line widths of the lines formed by performing the etching processmay vary depending on a gap between adjacent lines (pattern gap) inaddition to the adhesion coefficient. That is, the line widths of thelines formed on the wafer may vary depending on both the temperature ofthe wafer and the pattern gap.

In this case, it is difficult to independently control the line widthsof the lines in an area of a large pattern gap (hereinafter, referred toas “sparse area”) and an area of a small pattern gap (hereinafter,referred to as “dense area”) only by adjusting the temperature of thewafer. However, it may be possible to independently control the linewidths of the lines in the sparse area and the dense area only byadjusting a supply amount or composition ratio of a processing gas.Accordingly, there has been suggested a plasma etching apparatus thatindependently controls the line widths of the lines in a sparse area anda dense area by adjusting a temperature distribution in a surface of awafer and a supply amount or composition ratio of a processing gas (see,for example, Patent Document 2).

-   Patent Document 1: Japanese Translation of PCT Application No.    2008-532324-   Patent Document 2: Japanese Patent Laid-open Publication No.    2007-081216

However, in case of using the above-described plasma etching apparatusesto perform a plasma etching process, there are some problems as follows.

In the example disclosed in Patent Document 1, if a uniform patternhaving only a dense area is required to be formed, it is possible toperform an etching process with high uniformity in line widths of thelines formed on a wafer. However, as described above, when a patternhaving both a sparse area and a dense area is required, it is impossibleto perform an etching process with high uniformity in line widths of thelines formed on a wafer.

In the example disclosed in Patent Document 2, even when a patternhaving a sparse area and a dense area is formed, it is possible toperform an etching process with high uniformity in line widths of linesformed on a wafer. However, if a supply amount of a processing gas aswell as a composition ratio thereof is adjusted, there is a change inboth a supply amount of radicals and a supply amount of ions. The ionsmove straightforward and mainly contribute to an etching rate. Thus, itis difficult to control the etching rate to a required level bycontrolling the supply amount or composition ratio of the processinggas. Consequently, line widths and heights of the lines in the surfaceof the wafer cannot be uniformed and cross sections of the lines cannotbe uniformed.

By way of example, if the mask film includes an organic film, as aprocessing gas for etching the organic film, it may be possible to use aprocessing gas such as an oxygen gas (O₂) having a low adhesioncoefficient or a low reaction rate between the radicals and the maskfilm. In case of using the processing gas having the radicals of the lowreaction rate, even if the temperature of the wafer and the supplyamount or composition ratio of the processing gas are adjusted within atypical variable range, an amount of reacted radicals is hardly changedand the line widths of the lines cannot be controlled.

BRIEF SUMMARY OF THE INVENTION

In view of the foregoing, the present disclosure provides a plasmaetching method and a plasma etching apparatus that independently controldistributions of line widths and heights of lines in a surface of awafer and performs an etching process with high uniformity in crosssectional shapes of lines when the lines are formed by etching a layeredmask film including an inorganic film and an organic film or whenmultiple kinds of line groups having various gaps between adjacent linesare formed by etching a mask film.

In order to solve the above-described problems, the present disclosureprovides the following features.

In accordance with one aspect of the present disclosure, there isprovided a plasma etching method for performing a plasma etching on asubstrate by irradiating plasma containing charged particles and neutralparticles to the substrate. The plasma etching method includescontrolling a distribution of reaction amounts between the substrate andthe neutral particles in a surface of the substrate by adjusting atemperature distribution in the surface of the substrate supported by asupport; and controlling a distribution of irradiation amounts of thecharged particles in the surface of the substrate by adjusting a gapbetween the substrate supported by the support and an electrode providedso as to face the support.

In accordance with another aspect of the present disclosure, there isprovided a plasma etching apparatus configured to perform a plasmaetching on a substrate by irradiating plasma containing chargedparticles and neutral particles to the substrate. The plasma etchingapparatus includes a support capable of supporting the substrate; anelectrode provided so as to face the support; a temperature distributionadjusting unit capable of adjusting a temperature distribution in asurface of the substrate supported by the support; a gap adjusting unitcapable of adjusting a gap between the substrate supported by thesupport and the electrode; and a controller capable of controlling adistribution of reaction amounts between the substrate and the neutralparticles in the surface of the substrate by adjusting the temperaturedistribution by the temperature distribution adjusting unit and capableof controlling a distribution of irradiation amounts of the chargedparticles in the surface of the substrate by adjusting the gap by thegap adjusting unit.

In accordance with the present disclosure, it is possible toindependently control distributions of widths and heights of lines in asurface of a wafer and it is also possible to perform an etching processwith high uniformity in cross sectional shapes of lines when the linesare formed by etching a layered mask film including an inorganic filmand an organic film or when multiple kinds of line groups having variousgaps between adjacent lines are formed by etching a mask film.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments will be described inconjunction with the accompanying drawings. Understanding that thesedrawings depict only several embodiments in accordance with thedisclosure and are, therefore, not to be intended to limit its scope,the disclosure will be described with specificity and detail through useof the accompanying drawings, in which:

FIG. 1 is a cross sectional view showing a schematic configuration of aplasma etching apparatus in accordance with a first embodiment andshowing a status of an upper electrode located at a retreat position;

FIG. 2 is a cross sectional view showing a schematic configuration ofthe plasma etching apparatus in accordance with the first embodiment andshowing a status of the upper electrode located at a process position;

FIGS. 3A and 3B provide explanatory diagrams simply showing an upperelectrode driving unit;

FIG. 4 is a transversal cross-sectional view of the upper electrode;

FIG. 5 is a diagram for explaining a schematic configuration of a gassupply apparatus;

FIG. 6 is a flowchart for explaining a sequence of processes of a plasmaetching method in accordance with the first embodiment;

FIGS. 7A to 7E are cross sectional views schematically showing waferstates in each process of the plasma etching method in accordance withthe first embodiment;

FIGS. 8A to 8C are graphs showing distributions of etching rates ER in alongitudinal direction on a surface of a wafer when a gap G is adjusted;

FIGS. 9A to 9D are graphs schematically showing temperature dependencyof line widths CD of line groups and gap dependency of an etching rateER in a longitudinal direction during a second mask film etchingprocess;

FIGS. 10A to 10D are graphs schematically showing temperature dependencyof line widths CD of line groups and gap dependency of an etching rateER in a longitudinal direction during a first mask film etching process;

FIG. 11 is a cross sectional view showing a schematic configuration of aplasma etching apparatus in accordance with a second embodiment andshowing a status of an upper electrode located at a retreat position;

FIG. 12 is a cross sectional view showing a schematic configuration ofthe plasma etching apparatus in accordance with the second embodimentand showing a status of the upper electrode located at a processposition;

FIGS. 13A and 13B provide explanatory diagrams simply showing an upperelectrode driving unit;

FIG. 14 is a transversal cross sectional view of the upper electrode;

FIG. 15 is a diagram for explaining a schematic configuration of a gassupply apparatus;

FIG. 16 is a flowchart for explaining a sequence of processes of aplasma etching method in accordance with the second embodiment;

FIGS. 17A to 17E are cross sectional views schematically showingstatuses of a wafer in each process of the plasma etching method inaccordance with the second embodiment; and

FIGS. 18A to 18C are graphs schematically showing temperature dependencyof line widths CD of line groups and gap dependency of an etching rateER in a longitudinal direction in the second embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present disclosure will be describedwith reference to the accompanying drawings.

First Embodiment

Referring to FIGS. 1 to 10D, a plasma etching method and a plasmaetching apparatus in accordance with a first embodiment of the presentdisclosure will be explained.

First of all, referring to FIGS. 1 and 2, a plasma etching apparatus inaccordance with the present embodiment will be explained. FIGS. 1 and 2are cross sectional views showing schematic configurations of the plasmaetching apparatus in accordance with the present embodiment. FIG. 1shows a configuration in which an upper electrode is located at aretreat position, and FIG. 2 shows a configuration in which the upperelectrode is located at a process position.

A plasma etching apparatus 100 in accordance with the present embodimentis configured as a parallel plate type plasma etching apparatus, forexample.

The plasma etching apparatus 100 includes a cylindrical chamber(processing vessel) 102 made of, for example, aluminum of which surfaceis anodically oxidized (alumite treated). The chamber 102 is grounded.

A susceptor support 104 formed in a substantially columnar shape isprovided at a bottom of the chamber 102 via an insulating plate 103 madeof ceramic. Further, provided on the susceptor support 104 is asusceptor 105 serving as a lower electrode. The susceptor 105 isconnected with a high pass filter HPF 105 a.

The susceptor 105 is formed to have a protruded circular plate shape inan upper central area thereof, and an electrostatic chuck 111 havingsubstantially the same size as a wafer W is provided on the susceptor105. The electrostatic chuck 111 is formed of an insulating memberhaving an electrostatic electrode 112 embedded therein. Theelectrostatic chuck 111 is made of a circular plate-shaped ceramicmaterial, and the electrostatic electrode 112 is connected with a DCpower supply 113. If a positive DC voltage is applied to theelectrostatic electrode 112, a negative potential is generated at asurface of the wafer W on the electrostatic chuck 111's side(hereinafter, referred to as “rear surface”), so that there is generateda potential difference between the electrostatic electrode 112 and therear surface of the wafer W. The wafer W is attracted to and held on theelectrostatic chuck 111 by Coulomb force or Johnsen-Rahbek force causedby the potential difference. By way of example, a DC voltage of about1.5 kV is applied to the electrostatic chuck 111 from the DC powersupply 113 connected with the electrostatic electrode 112. Thus, thewafer W is electrostatically attracted to the electrostatic chuck 111.

Further, the susceptor support 104 and the susceptor 105 serve as asupporting member of the present disclosure.

The susceptor 105 is connected with a first high frequency power supply114 via a first matching unit 115 and a second high frequency powersupply 116 via a second matching unit 117. The first high frequencypower supply 114 applies a bias power, which is a high frequency powerhaving a relatively low frequency of, for example, about 13.6 MHz, tothe susceptor 105. The second high frequency power supply 116 applies apower for plasma generation, which is a high frequency power having arelatively high frequency of, for example, about 40 MHz, to thesusceptor 105. The susceptor 105 applies the power for plasma generationto the inside of the chamber 102.

Furthermore, provided through the insulating plate 103, the susceptorsupport 104, the susceptor 105, and the electrostatic chuck 111 is a gaspassage 118 for supplying a heat transfer medium (for example, abackside gas such as a He gas) to the rear surface of the wafer W as atarget object to be processed. Heat is transferred between the susceptor105 and the wafer W through this heat transfer medium, so that the waferW is maintained at a predetermined temperature.

An annular focus ring 119 is provided at an upper periphery of thesusceptor 105 so as to surround the wafer W supported on theelectrostatic chuck 111. The focus ring 119 is made of a dielectricmaterial such as ceramic or quartz or a conductive material such assingle crystalline silicon which is the same as a material of the waferW. Therefore, a distribution region of the plasma is extended from thewafer W to the focus ring 119, so that plasma density above an outerperipheral area of the wafer W can be maintained at substantially thesame level as plasma density above a central area of the wafer W. Thus,plasma etching uniformity in the surface of the wafer W can be improved.

There will be explained a temperature distribution adjusting unit 106which adjusts a temperature distribution in the surface of the wafer Wsupported on the susceptor 105. The temperature distribution adjustingunit 106 includes heaters 106 a and 106 b, heater power supplies 106 cand 106 d, thermometers 106 e and 106 f, and coolant paths 107 a and 107b.

Within the susceptor support 104, the central heater 106 a is providedat a central area and the outer peripheral heater 106 b is provided atan outer peripheral area. The central heater 106 a is connected with thecentral heater power supply 106 c and the outer peripheral heater 106 bis connected with the outer peripheral heater power supply 106 d. Eachof the central heater power supply 106 c and the outer peripheral heaterpower supply 106 d independently controls a power applied to the centralheater 106 a and the outer peripheral heater 106 b, so that it ispossible to control a temperature distribution of the susceptor support104 and the susceptor 105 in a radial direction. Thus, it is possible tocontrol a temperature distribution of the wafer W in a radial direction.

Further, within the susceptor support 104, the central thermometer 106 eand the outer peripheral thermometer 106 f are provided. The centralthermometer 106 e and the outer peripheral thermometer 106 f measuretemperatures of the central area and the outer peripheral area of thesusceptor support 104. Thus, temperatures at a central area and an outerperipheral area of the wafer W can be calculated. The temperaturesmeasured by the central thermometer 106 e and the outer peripheralthermometer 106 f are transmitted to an apparatus controller 190. Theapparatus controller 190 adjusts output of the central heater powersupply 106 c and the outer peripheral heater power supply 106 d suchthat the wafer W's temperature calculated from the measured temperaturesbecomes a target temperature.

Furthermore, within the susceptor support 104, the central coolant path107 a may be provided at the central area and the outer peripheralcoolant path 107 b may be provided at the outer peripheral area. By wayof example, cooling water and fluorocarbon-based coolant havingdifferent temperatures from each other may be circulated in the coolantpaths 107 a and 107 b, respectively. In this case, a coolant isintroduced to the central coolant path 107 a through a central inletline 108 a; circulated in the central coolant path 107 a; and thendischarged through a central outlet line 109 a. Meanwhile, a coolant isintroduced to the outer peripheral coolant path 107 b through an outerperipheral inlet line 108 b; circulated in the outer peripheral coolantpath 107 b; and then discharged through an outer peripheral outlet line109 b.

A temperature of the susceptor 105 is adjusted by heating by the heaters106 a and 106 b and cooling by the coolants. Therefore, the wafer W isadjusted to a preset temperature by a heat transfer from the susceptor105 as well as a radiation heat transfer from the plasma or irradiationof the ions contained in the plasma. In the present embodiment, thesusceptor support 104 includes the central heater 106 a and the centralcoolant path 107 a at the central area and the outer peripheral heater106 b and the outer peripheral coolant path 107 b at the outerperipheral area. Therefore, the temperatures at the central area and theouter peripheral area of the wafer W can be adjusted independently, andthe temperature distribution in the surface of the wafer W can beadjusted.

There may be a non-illustrated space between the central heater 106 aand the outer peripheral heater 106 b or between the central coolantpath 107 a and the outer peripheral coolant path 107 b, and the spacemay serve as a heat insulating layer. The heat insulating layerthermally isolates the central heater 106 a from the outer peripheralheater 106 b or the central coolant path 107 a from the outer peripheralcoolant path 107 b so that it is easy to make a great temperaturedifference between the central area of the wafer W and the outerperipheral area of the wafer W.

An upper electrode 120 facing the susceptor 105 in parallel is providedabove the susceptor 105. The upper electrode 120 can be moved in onedirection, for example, in a vertical direction, by an upper electrodedriving unit 200. Since the upper electrode 120 can be moved in thevertical direction, a thickness of a space between the upper electrode120 and the susceptor 105, i.e., a distance G (hereinafter, referred toas “gap”) between the upper electrode 120 and the susceptor 105 can beadjusted. By adjusting the gap G, plasma can be distributedappropriately in the space between the upper electrode 120 and thesusceptor 105 in the chamber 102 as described below. Further, it ispossible to adjust a distribution of a plasma irradiation amount to thesurface of the wafer W supported on the susceptor 105.

A maximum value of a vertical moving amount of the upper electrode 120driven by the upper electrode driving unit 200 can be set to be, forexample, about 70 mm. In this case, the gap G can be adjusted within arange of about 20 mm to about 90 mm.

The plasma etching apparatus may have a configuration rotated 90 degreesfrom the configurations illustrated in FIGS. 1 and 2 or may have anupside-down configuration thereof. Further, the upper electrode 120serves as an electrode of the present disclosure. The upper electrodedriving unit 200 serves as a gap adjusting unit of the presentdisclosure.

The upper electrode 120 is supported by an upper inner wall of thechamber 102 via a bellows 122. The bellows 122 is fixed to the upperinner wall of the chamber 102 via an annular upper flange 122 a by afixing member such as a bolt and fixed to a surface of the upperelectrode 120 via an annular lower flange 122 b by a fixing member suchas a bolt.

The upper electrode 120 is connected with a DC power supply 123.Further, the upper electrode 120 is connected with a low pass filter LPF124.

A bottom area of the chamber 102 is connected with a gas exhaust pipe131 and the gas exhaust pipe 131 is connected with a gas exhaust unit135. The gas exhaust unit 135 includes a vacuum pump such as aturbo-molecular pump and adjusts the internal pressure of the chamber102 to a preset depressurized atmosphere (for example, about 0.67 Pa orless). Further, a gate valve 132 is installed at a sidewall of thechamber 102. By opening the gate valve 132, the wafer W can be loadedinto the chamber 102 and unloaded from the chamber 102. Furthermore, byway of example, when the wafer W is transferred, a transfer arm may beused.

Hereinafter, a configuration of the upper electrode driving unit 200will be explained in detail with reference to FIGS. 3A and 3B. FIGS. 3Aand 3B provide explanatory diagrams simply showing the upper electrodedriving unit. To be specific, FIG. 3A shows the upper electrode drivingunit located at a retreat position, and FIG. 3B shows the upperelectrode driving unit located at a process position.

The upper electrode driving unit 200 includes a substantiallycylindrical support member 204 which supports the upper electrode 120.The support member 204 is fixed at an approximate center of the top ofthe upper electrode 120 by a bolt or the like.

The support member 204 is installed so as to be allowed to enter a hole102 a formed at an approximate center of an upper wall of the chamber102. To be specific, an outer surface of the support member 204 issupported at an inner wall of the hole 102 a of the chamber 102 via aslide mechanism 210.

By way of example, the slide mechanism 210 includes a guide member 216fixed to a vertical part of a fixing member 214 having an L-shaped crosssection at an upper area of the chamber 102; and a rail 212 provided onthe outer surface of the support member 204 in one direction (verticaldirection in the present embodiment) and supported by the guide member216 so as to be slidably moved.

The fixing member 214 that fixes the guide member 216 of the slidemechanism 210 has a horizontal part which is fixed at the upper area ofthe chamber 102 via an annular horizontal position adjusting plate 218.The horizontal position adjusting plate 218 is configured to adjust ahorizontal position of the upper electrode 120. By way of example, thehorizontal position adjusting plate 218 is fixed to the chamber 102 by amultiple number of bolts arranged at a same interval in acircumferential direction of the horizontal position adjusting plate218, and an inclination of the horizontal position adjusting plate 218with respect to a horizontal direction may be adjusted by a protrudedheight of the bolts. By adjusting the inclination of the horizontalposition adjusting plate 218 with respect to the horizontal direction,an inclination of the guide member 216 of the slide mechanism 210 withrespect to a vertical direction can be adjusted. Therefore, aninclination of the upper electrode 120 supported via the guide member216 with respect to a horizontal direction can be adjusted.Consequently, a horizontal position of the upper electrode 120 can bemaintained all the time by a simple manipulation.

A pneumatic cylinder 220 for driving the upper electrode 120 is providedabove the chamber 102 via a cylindrical body 201. A lower end of thecylindrical body 201 is airtightly sealed so as to cover the hole 102 aof the chamber 102 and an upper end of the cylindrical body 201 isairtightly sealed with a lower end of the pneumatic cylinder 220.

The pneumatic cylinder 220 includes a rod 202 which can be moved in onedirection. A lower end of the rod 202 is connected with an approximatecenter of the top of the support member 204 by a bolt or the like. Bydriving the rod 202 of the pneumatic cylinder 220, the upper electrode120 is moved by the support member 204 in one direction along with theslide mechanism 210. The rod 202 is formed in a cylinder shape and aninner space of the rod 202 communicates with a center hole formed at anapproximate center of the support member 204 so as to be opened to theatmosphere. Therefore, a line for grounding the upper electrode 120 viathe low pass filter LPF 124 and a power supply line for applying a DCvoltage from the DC power supply 123 to the upper electrode 120 may beconnected with the upper electrode 120 via the inner space of the rod202 and the center hole of the support member 204.

By way of example, provided at a side area of the pneumatic cylinder 220is a linear encoder 205 as a position detection unit for detecting aposition of the upper electrode 120. Meanwhile, provided at an upper endof the rod 202 of the pneumatic cylinder 220 is an upper end member 207having an extended part 207 a extended from the rod 202 in a lateraldirection. The extended part 207 a of the upper end member 207 is incontact with a detector 205 a of the linear encoder 205. Since the upperend member 207 is moved along with the upper electrode 120, a positionof the upper electrode 120 can be detected by the linear encoder 205.

The pneumatic cylinder 220 includes a cylinder main body 222 between anupper support plate 224 and a lower support plate 226. Provided on anouter surface of the rod 202 is an annular partition member 208 whichdivides the inside of the pneumatic cylinder 220 into an upper space 232and a lower space 234.

As depicted in FIGS. 3A and 3B, compressed air is introduced from anupper port 236 of the upper support plate 224 into the upper space 232of the pneumatic cylinder 220. Further, compressed air is introducedfrom a lower port 238 of the lower support plate 226 into the lowerspace 234 of the pneumatic cylinder 220. By controlling an amount of theair introduced from the upper port 236 and the lower port 238 into theupper space 232 and the lower space 234, respectively, it is possible tocontrol the rod 202 to be moved in one direction (vertical direction inthis embodiment). The amount of the air introduced to the pneumaticcylinder 220 is controlled by a pneumatic circuit 300 provided in thevicinity of the pneumatic cylinder 220.

The upper electrode driving unit 200 includes a controller 290 and thecontroller 290 is connected with the apparatus controller 190. A controlsignal from the apparatus controller 190 is transmitted to thecontroller 290 and each component of the upper electrode driving unit200 is controlled by the controller 290.

Hereinafter, there will be explained a supply amount distributionadjusting unit 130 that adjusts a distribution of a supply amount of aplasma gas supplied to the wafer W supported on the susceptor 105. Thesupply amount distribution adjusting unit 130 includes a shower head 140configured as one body with the upper electrode 120, and a gas supplyapparatus 150.

Referring to FIGS. 1, 2 and 4, a configuration of the shower head 140will be explained. FIG. 4 is a transversal cross sectional view of theupper electrode.

The shower head 140 is configured to supply a mixed gas onto the wafer Wsupported on the susceptor 105. The shower head 140 includes a circularelectrode plate 141 (upper electrode 120) having a multiple number ofgas discharge holes 141 a and an electrode support body 142 whichsupports an upper surface of the electrode plate 141 and is detachabletherefrom. The electrode support body 142 is formed in a circular plateshape having the same diameter as the electrode plate 141 and includes acircular buffer room 143 therein. By way of example, as depicted in FIG.4, in the buffer room 143, an annular partition wall member 145 formedof an O-ring is installed and divides the buffer room 143 into a firstbuffer room 143 a on a central side and a second buffer room 143 b on anouter peripheral side. The first buffer room 143 a faces a central areaof the wafer W on the susceptor 105 and the second buffer room 143 bfaces an outer peripheral area of the wafer W on the susceptor 105.Bottom surfaces of the respective buffer rooms 143 a and 143 bcommunicate with the gas discharge holes 141 a, and the mixed gas may bedischarged from the first buffer room 143 a toward the central area ofthe wafer W and from the second buffer room 143 b toward the outerperipheral area of the wafer W. Further, the mixed gas is supplied tothe buffer rooms 143 a and 143 b by the gas supply apparatus 150.

Hereinafter, referring to FIGS. 1, 2 and 5, the gas supply apparatus 150will be explained. FIG. 5 is a diagram for explaining a schematicconfiguration of the gas supply apparatus.

As depicted in FIG. 5, the gas supply apparatus 150 includes a first gasbox 161 which accommodates a multiple number of, for example, three gassupply sources 160 a, 160 b, and 160 c and a second gas box 163 whichaccommodates a multiple number of, for example, two additional gassupply sources 162 a and 162 b. In the present embodiment, by way ofexample, a fluorocarbon-based fluorine compound as a processing gas, forexample, C_(X)F_(Y) such as CF₄, C₄F₆, C₄F₈, and C₅F₈ is sealed in thegas supply source 160 a. Further, by way of example, an oxygen (O₂) gasas a gas for controlling adhesion of a CF-based reaction product issealed in the gas supply source 160 b. A rare gas as a carrier gas, forexample, an Ar gas is sealed in the gas supply source 160 c. By way ofexample, a C_(X)F_(Y) gas capable of promoting an etching process issealed in the additional gas supply source 162 a, and an oxygen (O₂) gascapable of controlling adhesion of a CF-based reaction product is sealedin the additional gas supply source 162 b.

Each of the gas supply sources 160 a to 160 c of the first gas box 161is connected with a mixing line 170 where various gases from each of thegas supply sources 160 a to 160 c are joined and mixed together. In themixing line 170, a mass flow controller 171 for adjusting a flow rate ofa gas from each of the gas supply sources 160 a to 160 c is provided foreach gas supply source. The mixing line 170 is connected with a firstbranch line 172 and a second branch line 173 which divide the mixed gasmixed at the mixing line 170. The first branch line 172 is connectedwith the first buffer room 143 a of the shower head 140. The secondbranch line 173 is connected with the second buffer room 143 b of theshower head 140.

A pressure adjusting unit 174 is installed on the first branch line 172.In the same manner, a pressure adjusting unit 175 is installed on thesecond branch line 173. The pressure adjusting unit 174 includes apressure gauge 174 a and a valve 174 b. Likewise, the pressure adjustingunit 175 includes a pressure gauge 175 a and a valve 175 b. Ameasurement result measured by the pressure gauge 174 a of the pressureadjusting unit 174 and a measurement result measured by the pressuregauge 175 a of the pressure control unit 175 may be outputted to apressure control apparatus 176. The pressure control apparatus 176adjusts an opening/closing degree of each valve 174 b or 175 b based onthe measurement results of the pressure gauges 174 a and 175 a andcontrols a pressure ratio, i.e., a flow rate ratio of the mixed gas inthe first branch line 172 and the second branch line 173. Further, whensetting a supplied gas, the pressure control apparatus 176 may adjuststhe pressure ratio of the mixed gas flowing through the first branchline 172 and the second branch line 173 to a preset target pressureratio in a state where an additional gas is not supplied from the secondgas box 163, which will be described later, to the second branch line173 and the pressure control apparatus 176 may set opening/closingdegrees of the valves 174 b and 175 b in that state.

Each additional gas supply source 162 a or 162 b of the second gas box163 is connected with an additional gas supply line 180 communicatingwith, for example, the second branch line 173. By way of example, theadditional gas supply line 180 is connected with each additional gassupply source 162 a or 162 b and the additional gas supply line 180 isconnected with the second branch line 173 on the way. The additional gassupply line 180 is connected with a downstream side of the pressureadjusting unit 175. On the additional gas supply line 180, a mass flowcontroller 181 for controlling a flow rate of an additional gas fromeach additional gas supply source 162 a or 162 b is provided for eachadditional gas supply source. With this configuration, the additionalgases from the second gas box 163 may be selected and mixed together tobe supplied to the second branch line 173.

Operations of the mass flow controller 171 in the first gas box 161 andthe mass flow controller 181 in the second gas box 163 are controlledby, for example, the apparatus controller 190, which will be describedlater, of the plasma etching apparatus 100. Accordingly, the apparatuscontroller 190 may control a start and a stop of supply of various gasesfrom the first gas box 161 and the second gas box 163, and controlsupply amounts of various gases.

Further, the second gas box 163 and the additional gas supply line 180may be omitted from the gas supply apparatus 150.

The plasma etching apparatus 100 includes the apparatus controller 190.The apparatus controller 190 includes a non-illustrated operationprocessing unit such as a CPU and a non-illustrated storage medium suchas a hard disk. The apparatus controller 190 controls an operation ofeach component such as the first high frequency power supply 114, thesecond high frequency power supply 116, the temperature distributionadjusting unit 106, the upper electrode driving unit 200, or the supplyamount distribution adjusting unit 130. Further, by way of example, whenthe apparatus controller 190 controls the operation of each component,the CPU of the apparatus controller 190 controls the operation of eachcomponent according to a program corresponding to each etching processwhich is stored in, for example, the hard disk of the apparatuscontroller 190.

The apparatus controller 190 serves as a controller of the presentdisclosure.

Hereinafter, referring to FIG. 6 and FIGS. 7A to 7E, there will beexplained a plasma etching method using the plasma etching apparatus100. FIG. 6 is a flowchart for explaining a sequence of processes of aplasma etching method in accordance with the present embodiment. FIGS.7A to 7E are cross sectional views schematically showing statuses of awafer in each process of the plasma etching method in accordance withthe present embodiment.

As depicted in FIG. 6, the plasma etching method in accordance with thepresent embodiment includes a resist pattern forming process (step S11),an anti-reflective coating etching process (step S12), a second maskfilm etching process (step S13), a first mask film etching process (stepS14), and an etching target film etching process (step S15).

Further, the second mask film etching process (step S13) and the firstmask film etching process (step S14) are included in an etching processof the present disclosure.

Above all, the resist pattern forming process (step S11) is performed.In the resist pattern forming process (step S11), a resist patternhaving line groups 16 a and 16 b formed of a resist film 16 is formed ona surface of a wafer W on which a second mask film 14 is already formedvia a first mask film 13. FIG. 7A shows a wafer state in the resistpattern forming process (step S11).

Herein, a line group is a structure extended in a certain direction andspaced apart from an adjacent line group in a direction orthogonal tothe extended direction when viewed from the top.

There is prepared in advance a substrate in which an insulating film 11,an etching target film 12, a first mask film 13, a second mask film 14,and an anti-reflective coating 15 are formed in sequence from thesurface of a wafer 10 made of, for example, a silicon.

The etching target film 12 is a film to be etched finally in the plasmaetching method in accordance with the present embodiment. By way ofexample, the insulating film may be a silicon oxide (SiO₂) film made of,e.g., tetraethoxysilane (TEOS) serving as a gate insulating film, andthe etching target film 12 after an etching process may be a polysiliconfilm serving as a gate electrode.

The first mask film 13, to which a shape of the second mask film 14 asan upper layer is transferred, serves as a hard mask when the etchingtarget film 12 as a lower layer is etched. The first mask film 13 mayhave a high selectivity as compared to the etching target film 12 whenthe etching target film 12 is etched. That is, a ratio of an etchingrate of the etching target film 12 to an etching rate of the first maskfilm 13 may be high. For example, as the first mask film 13, it may bepossible to use an inorganic film such as a SiN film and a SiON film. Athickness of the first mask film 13 may be set to be, for example, about200 nm.

The second mask film 14, to which a resist pattern shape of the resistfilm 16 as an upper layer is transferred, serves as a mask when thefirst mask film 13 as a lower layer is etched. The second mask film 14has a high selectivity as compared to the first mask film 13 when thefirst mask film 13 is etched. That is, a ratio of the etching rate ofthe first mask film 13 to an etching rate of the second mask film 14 ishigh. By way of example, as the second mask film 14, it may be possibleto use an organic film made of a variety of organic materials such asamorphous carbon formed by chemical vapor deposition CVD, polyphenolformed by spin-on techniques or a photoresist such as a i-line resist. Athickness of the second mask film 14 may be set to be, for example,about 280 nm.

The anti-reflective coating 15 serves as an antireflection film when aphotolithography process is performed on the resist film 16 formed onthe anti-reflective coating 15. For example, as the anti-reflectivecoating 15, it is possible to use a film made of C_(x)H_(y)O_(z)referred to as an organic BARC. A thickness of the anti-reflectivecoating 15 may be set to be, for example, 80 nm.

The resist film 16 is formed on the wafer 10 on which theabove-described films from the insulating film 11 to the anti-reflectivecoating 15 are layered. A pattern of the formed resist film 16 isexposed to lights and developed, so that the resist pattern having theline groups 16 a and 16 b formed of the resist film 16 is formed. Asdepicted in FIG. 7A, a resist pattern formed of the resist film 16 haslines of line widths CD and heights H. On the left of FIG. 7A, there isformed an area A1 (hereinafter, referred to as “dense area”) where thelines 16 a are arranged at a relatively small distance D1 and on theright of FIG. 7A, there is formed an area A2 (hereinafter, referred toas “sparse area”) where the lines 16 b are arranged at a relativelylarge distance D2 (larger than the distance D1). The line groups 16 aand 16 b serve as a mask when the anti-reflective coating 15 and thesecond mask film 14 are etched. As the resist film 16, it may bepossible to use, for example, an ArF resist. Further, a thickness of theresist film 16 may be set to be, for example, about 170 nm.

Herein, a line width CD is a width of a line in a direction orthogonalto an extended direction of the line.

The line in the dense area A1 serves as a first line of the presentdisclosure. Further, a line in the sparse area A2 serves as a secondline of the present disclosure.

After the resist pattern forming process (step S11) and before theanti-reflective coating etching process (step S12), a slimming processor a trimming process may be performed, so that a line width adjustingprocess for reducing line widths CD of the line groups 16 a and 16 b ofthe resist film 16 may be performed. If the line width adjusting processis performed, a line width CD indicates a width of the line after theline width adjusting process.

Then, the anti-reflective coating etching process (step S12) isperformed. In the anti-reflective coating etching process (step S12),plasma is irradiated onto the wafer 10 and the anti-reflective coating15 is etched by the irradiated plasma by using the line groups 16 a and16 b formed of the resist film 16 as a mask. FIG. 7B shows a status of awafer in the anti-reflective coating etching process (step S12).

In response to a control signal from the apparatus controller 190, theupper electrode driving unit 200 is moved in a vertical direction and adistance between the susceptor 105 and the upper electrode 120 is set tobe a preset gap G. Thereafter, in response to a control signal from theapparatus controller 190, a predetermined supply amount FLI of aprocessing gas is supplied to the central area of the wafer W supportedon the susceptor 105 in the chamber 102 from the gas supply apparatus150 via the first branch line 172 and the first buffer room 143 a of theshower head 140. Further, in response to a control signal from theapparatus controller 190, a predetermined supply amount FLO of aprocessing gas is supplied to the outer peripheral area of the wafer Wsupported on the susceptor 105 in the chamber 102 from the gas supplyapparatus 150 via the second branch line 173 and the second buffer room143 b of the shower head 140. Then, in response to a control signal fromthe apparatus controller 190, a first high frequency power is appliedfrom the first high frequency power supply 114 and a second highfrequency power is applied from the second high frequency power supply116. The processing gas introduced into the chamber 102 is excited intoplasma by the high frequency power applied into the chamber 102 from thefirst high frequency power supply 114 and the second high frequencypower supply 116 which are connected with the susceptor 105.

The excited plasma contains ions, electrons, and radicals. The ions areattracted toward the wafer 10 supported on the susceptor 105 by a biasvoltage generated between the upper electrode 120 and the susceptor 105and react with the surface of the wafer 10, so that the wafer 10 isetched. Meanwhile, the radicals are not attracted by a bias potentialbut diffuse to the surface of the wafer 10 and react with the surface ofthe wafer 10, so that the wafer 10 is etched. Consequently, theanti-reflective coating 15 is etched using the line groups 16 a and 16 bformed of the resist film 16 as a mask.

Further, the ions serve as charged particles of the present disclosureand the radicals serve as neutral particles of the present disclosure.

In the anti-reflective coating etching process (step S12), as theprocessing gas, it may be possible to use a mixed gas of a CF-based gassuch as CF₄, C₄F₈, CHF₃, CH₃F, and CH₂F₂ with an Ar gas, or the mixedgas further including an oxygen gas if necessary.

Subsequently, the second mask film etching process (steps S13) isperformed. In the second mask film etching process (steps S13), thesecond mask film 14 is etched by plasma irradiated to the wafer 10 usingline groups 15 a and 15 b formed of the resist film 16 and theanti-reflective coating 15 as a mask, so that line groups 14 a and 14 bincluding the second mask film 14 are formed. FIG. 7C shows a waferstate in the second mask film etching process (step S13).

In the second mask film etching process (step S13), a temperaturedistribution in the surface of the wafer 10 supported on the susceptor105 is adjusted and a distribution of a supply amount of the processinggas supplied to the wafer 10 in the surface of the wafer 10 is adjusted.By these adjustments, a distribution of a reaction amount between theradicals of the plasma in the surface of the wafer 10 and the surface ofthe wafer 10 is controlled. By controlling the distribution of thereaction amounts it is possible to control a distribution of line widthsCD of the line groups 14 a and 14 b in the surface of the wafer 10.

In response to a control signal from the apparatus controller 190 to thetemperature distribution adjusting unit 106, temperatures of the centraland outer peripheral thermometers 106 e and 106 f are adjusted topredetermined temperatures TI and TO, respectively. Further, in responseto the control signal from the apparatus controller 190 to thetemperature distribution adjusting unit 106, the central heater 106 aand the outer peripheral heater 106 b are controlled independently.Consequently, it is possible to set the temperature TI at the centralarea of the wafer 10 to be different from the temperature TO at theouter peripheral area of the wafer 10, and, thus, the temperaturedistribution in the surface of the wafer 10 can be adjusted.

Further, in response to a control signal from the apparatus controller190 to the supply amount distribution adjusting unit 130, a gas from thefirst gas box 161 is supplied to the first buffer room 143 a and thesecond buffer room 143 b of the shower head 140 via each of the firstbranch line 172 and the second branch line 173. Since the flow rates inthe first branch line 172 and the second branch line 173 are adjusted bythe pressure adjusting units 174 and 175, the flow rate FLI of theprocessing gas supplied to the central area of the wafer 10 can be setto be different from the flow rate FLO of the processing gas supplied tothe outer peripheral area of the wafer 10. Consequently, it is possibleto adjust the distribution of supply amounts of the processing gas inthe surface of the wafer 10.

As described above, by adjusting the temperature distribution and thedistribution of supply amounts of the processing gas in the surface ofthe wafer 10, it is possible to control the distribution of line widthsCD of the line groups 14 a and 14 b formed of the second mask film 14 inthe surface of the wafer 10.

In the second mask film etching process (step S13), in response to acontrol signal from the apparatus controller 190 to the upper electrodedriving unit 200, a gap G between the wafer 10 supported on thesusceptor 105 and the upper electrode 120 facing the wafer 10 isadjusted. By adjusting the gap G, it is possible to control adistribution of irradiation amounts of ions in the surface of the wafer10 and a distribution of etching rates ER in a longitudinal direction(depth direction). Further, by controlling the distribution of etchingrates ER in the longitudinal direction (depth direction), it is possibleto control a distribution of heights H of the line groups 14 a and 14 bin the surface of the wafer 10.

In the second mask film etching process (step S13), it may be possibleto use an oxygen (O₂) gas as the processing gas.

Thereafter, the first mask film etching process (step S14) is performed.In the first mask film etching process (step S14), the first mask film13 is etched by plasma irradiated to the wafer 10 using the line groups14 a and 14 b formed of the second mask film 14 as a mask, so that linegroups 13 a and 13 b including the first mask film 13 are formed. FIG.7D shows a status of a wafer in the first mask film etching process(step S14).

In the first mask film etching process (step S14), a temperaturedistribution in the surface of the wafer 10 supported on the susceptor105 is adjusted and a distribution of supply amounts of the processinggas supplied to the wafer 10 in the surface of the wafer 10 is adjusted.By these adjustments, a distribution of reaction amounts between theradicals of the plasma in the surface of the wafer 10 and the surface ofthe wafer 10 is controlled. By controlling the distribution of reactionamounts, it is possible to control a distribution of line widths CD ofthe line groups 13 a and 13 b in the surface of the wafer 10.

Further, in the first mask film etching process (step S14), in responseto a control signal from the apparatus controller 190 to the upperelectrode driving unit 200, a gap G between the wafer 10 supported onthe susceptor 105 and the upper electrode 120 provided so as to face thewafer 10 is adjusted. By adjusting the gap G, it is possible to controla distribution of irradiation amounts of ions in the surface of thewafer 10 and a distribution of etching rates ER in a longitudinaldirection (depth direction). Further, by controlling the distribution ofetching rates ER in the longitudinal direction (depth direction), it ispossible to control a distribution of heights H of the line groups 13 aand 13 b in the surface of the wafer 10.

In the first mask film etching process (step S14), as the processinggas, it may be possible to use a mixed gas of a CF-based gas such asCF₄, C₄F₈, CHF₃, CH₃F, and CH₂F₂ with an Ar gas, or the mixed gasfurther including an oxygen (O₂) gas if necessary.

There may be a following relationship between the second mask filmetching process (step S13) and the first mask film etching process (stepS14). That is, temperature dependency of a reaction amount between theradicals and a surface of the first mask film 13 in the first mask filmetching process (step S14) may be greater than temperature dependency ofa reaction amount between the radicals and a surface of the second maskfilm 14 in the second mask film etching process (step S13). That isbecause, as described below, if the relationship is satisfied, it isimpossible to independently control a distribution of line widths CD ofthe line groups and a distribution of heights H of the line groups inthe surface of the wafer 10 in the conventional method.

Then, the etching target film etching process (step S15) is performed.In the etching target film etching process (step S15), the etchingtarget film 12 is etched by plasma irradiated to the wafer 10 using theline groups 13 a and 13 b formed of the first mask film 13 as a mask, sothat line groups 12 a and 12 b including the etching target film 12 areformed. FIG. 7E shows a status of a wafer in the etching target filmetching process (step S15).

In the etching target film etching process (step S15), such control asperformed in the first mask film etching process (step S14) may beperformed. That is, by adjusting the temperature distribution and thedistribution of supply amounts of the processing gas in the surface ofthe wafer 10, it is possible to control a distribution of line widths CDof the line groups 12 a and 12 b in the surface of the wafer 10, and byadjusting the gap G between the upper electrode 120 and the wafer 10, itis possible to control a distribution of heights H of the line groups 12a and 12 b in the surface of the wafer 10.

In the etching target film etching process (step S15), as the processinggas, it may be possible to use a mixed gas of a CF-based gas such asCF₄, C₄F₈, CHF₃, CH₃F, and CH₂F₂ with an Ar gas, or the mixed gasfurther including an oxygen (O₂) gas if necessary.

Hereinafter, there will be explained a case where a distribution of linewidths CD of lines and a distribution of heights H of the lines in asurface of a wafer are independently controlled and an etching processcan be performed with high uniformity in cross sectional shapes of lineswhen the etching process is performed on the wafer using the plasmaetching method in accordance with the present embodiment.

As described above, the plasma of the processing gas contains the ionsand the radicals. Since the ions are accelerated by the bias voltagegenerated between the upper electrode 120 and the susceptor 105 andirradiated to the wafer, an anisotropic etching process is mainlyperformed on the wafer. Therefore, the lines to be formed are mainlyetched in a longitudinal direction (depth direction). Meanwhile, theradicals are not accelerated by the bias voltage, and, thus, anisotropic etching process is mainly performed on the wafer. Therefore,the lines to be formed are mainly etched in a width direction. Further,a reaction product generated by a reaction between a surface of thewafer and the plasma may adhere to the lines again. Here, a line widthCD of the lines may vary depending on an adhesion coefficient whichindicates a probability that the reaction product adheres to the lineagain. Since the adhesion coefficient depends on a temperature of thewafer, the line width CD of the lines may vary depending on thetemperature of the wafer.

As described above, in the plasma etching process, an etching condition(parameter) controlling an etching rate ER in a vertical direction(longitudinal direction) is different from an etching condition(parameter) controlling a line width CD of the lines in the surface ofthe wafer.

When plasma is irradiated to the wafer, the parameter controlling theetching rate ER in the longitudinal direction includes an amount of ions(ion flux) approximately vertically incident to a surface of the waferper unit time; energy of ions; and an adsorption amount of radicalsadsorbed to the surface of the wafer. When the radicals are suppliedsufficiently, the most dominant parameter in controlling the etchingrate ER in the longitudinal direction is the ion flux. In order tocontrol a distribution of line widths CD of lines formed by an etchingprocess in the surface of the wafer, it is necessary to independentlycontrol a distribution of the ion flux and a distribution of reactionamounts of the radicals.

Herein, a method of controlling a distribution of an ion flux in thesurface of the wafer may include the following three methods: a methodof adjusting a distribution of a magnetic field by using a permanentmagnet or an electromagnet; a method of adjusting a distribution of anelectric field by dividing an electrode and adjusting impedance; and amethod of forming protrusions or recesses in the upper electrode oradjusting a distance (gap) between the upper electrode and the lowerelectrode.

Among these three methods of controlling the distribution of the ionflux, in accordance with the method of adjusting the distribution of themagnetic field, the distribution of the ion flux cannot be controlledstably. Especially, a magnetic field exists near the wafer, and, thus,arcing may occur easily. Further, in accordance with the method ofadjusting the distribution of the electric field by dividing anelectrode and adjusting impedance, the distribution of the ion fluxcannot be made substantially uniform.

Meanwhile, in accordance with the method of adjusting the gap G, the ionflux may be adjusted in a wide range. By adjusting the ion flux, it ispossible to control the distribution of etching rates ER in thelongitudinal direction in the surface of the wafer.

Hereinafter, referring to FIGS. 8A to 8C, gap dependency of an etchingrate ER in a longitudinal direction will be explained. FIGS. 8A to 8Care graphs showing distributions of etching rates ER in a longitudinaldirection in a surface of a wafer when a gap G is adjusted. The gaps Gin FIGS. 8A, 8B, and 8C are 30 mm, 50 mm, and 90 mm, respectively. InFIGS. 8A to 8C, a horizontal axis represents a distance X from a centerin a radial direction and a vertical axis represents an etching rate ERin a longitudinal direction. Further, a wafer of 300 mmØ is used.

As depicted in FIG. 8A, when a gap G is about 30 mm, an etching rate ERin a longitudinal direction is maximized at a central area of the waferand gradually decreased toward an outer peripheral area of the wafer andafter reaching a minimum value, the etching rate ER is slightlyincreased at the outer peripheral area. Thus, a distribution of etchingrates ER is not uniform in a surface of the wafer. In this case, anaverage of the etching rates ER in the longitudinal direction is about178.4 nm/min and a deviation is about 14.9%.

Meanwhile, as depicted in FIG. 8B, when a gap G is about 50 mm, anetching rate ER becomes more uniform in the surface of the waferalthough an etching rate ER in a longitudinal direction is increased atthe outer peripheral area of the wafer as compared to that in thecentral area of the wafer. In this case, an average of the etching ratesER in the longitudinal direction is about 208.3 nm/min and a deviationis about 12.6%.

Further, as depicted in FIG. 8C, when a gap G is about 90 mm, an etchingrate ER in a longitudinal direction becomes much more uniform in thesurface of the wafer. In this case, an average of the etching rates ERin the longitudinal direction is about 164.5 nm/min and a deviation isabout 7.3%.

As described above, by adjusting a gap G, it is possible to control adistribution of ion flux.

When the plasma is irradiated to the wafer, the ions contained in theplasma are substantially vertically incident to the surface of the waferand scarcely irradiated to sidewalls of the lines. Therefore, parameterscontrolling line widths CD of lines to be formed may include an amountof a polymer film formed on a surface of the sidewall of the line due toadhesion of the radicals to the sidewall and an etching amount of thesurface of the sidewall of the line due to a reaction between theradicals and the sidewall of the line.

Herein, a method of controlling a reaction amount of the radicals in thesurface of the wafer may include the following three methods: a methodof adjusting a distribution of a supply amount of a processing gassupplied to generate the radicals; a method of adjusting a distributionof a composition ratio of the processing gas supplied as a mixed gas;and a method of adjusting a temperature distribution in the surface ofthe wafer in order to adjust a reaction rate.

Among these three methods of controlling the distribution of reactionamounts of the radicals, in accordance with the method of adjusting thedistribution of the supply amount of the processing gas and the methodof adjusting the distribution of the composition ratio of the processinggas, it is impossible to locally adjust the supply amount and thecomposition ratio of the processing gas in the surface of the wafer. Forthis reason, it is also impossible to locally adjust the distribution ofthe reaction amount of the radicals.

Meanwhile, in accordance with the method of adjusting the temperaturedistribution of the wafer, even if various processing gases and variousradicals are used, it is possible to locally adjust the distribution ofreaction amounts of the radicals. Thus, it is possible to locallycontrol the distribution of line widths CD of the lines in the surfaceof the wafer.

To be specific, referring to Table 1, there will be explained a methodof independently controlling a distribution of an ion flux and adistribution of a reaction amount of radicals by using the method ofadjusting the gap G and the method of adjusting the temperaturedistribution of the wafer. Herein, as described below, the gap G and thetemperature distribution of the wafer are adjusted under conditions (A)and (B), and a deviation of line widths CD in the surface of the waferis calculated.

(A) Second Mask Film Etching Process (Step S13)

Material of second mask film: naphthalene (or polystyrene)

Thickness of second mask film: 280 nm

Internal pressure of film forming apparatus: 20 mTorr

High frequency power (40 mHz/13 MHz): 500/0 W

Potential of upper electrode: 0 V

Flow rate of processing gas: O₂=750 sccm

Processing time: 60 seconds

(B) First Mask Film Etching Process (Step S14)

Material of first mask film: silicon nitride (SiN)

Thickness of first mask film: 280 nm

Internal pressure of film forming apparatus: 75 mTorr

High frequency power (40 mHz/13 MHz): 500/0 W

Potential of upper electrode: 300 V

Flow rate of processing gas: CF₃/CF₄/Ar/O₂=125/225/600/60 sccm (here,CH₂F₂ of about 20 sccm may be added to outer peripheral area)

Processing time: 60 seconds

In the conditions (A) and (B), a flow rate of the processing gas is usedto adjust a supply amount of the processing gas, for example. However,it may be also possible to change a supply time of the processing gas byopening/closing a valve so as to adjust the supply amount of theprocessing gas without changing the flow rate of the processing gas.

Table 1 shows a deviation CD1σ of line widths in a dense area A1 when agap G, a temperature TI at a central area of the wafer, and atemperature TO at an outer peripheral area of the wafer are adjusted.Further, Table 1 shows an example where a ratio between a flow rate FLIof the processing gas at the central area and a flow rate FLO of theprocessing gas at the outer peripheral area is optimized in advance to50:50.

TABLE 1 Gap G (mm) 30 50 90 50 Central area 40 40 40 50 temperature TI(° C.) Outer peripheral area 40 40 40 40 temperature TO (° C.) Flow rateratio between 50:50 50:50 50:50 50:50 central flow rate FLI and outerperipheral flow rate FLO Deviation CD1σ (nm) 7.5 3.8 1.9 1.5 of linewidth CD at dense area A1 Deviation CD2σ (nm) 36.5 7.2 7.7 2.9 of linewidths CD at sparse area A2

As shown in Table 1, under the condition that the gap G is about 30 mm,the temperature TI at the central area is about 40° C., and thetemperature TO at the outer peripheral area is about 40° C., thedeviation CD1σ becomes as great as about 7.5 nm. Further, the deviationCD1σ is decreased to about 3.8 nm and about 1.9 nm by adjusting the gapG to about 50 mm and about 90 mm, respectively, without changing thecondition that the temperature TI at the central area is about 40° C.and the temperature TO at the outer peripheral area is about 40° C.

Furthermore, by adjusting the temperature TI at the central area and thetemperature TO at the outer peripheral area as well as the gap G, thedeviation CD1σ can be decreased to about 1.5 nm under the condition thatthe gap G is about 50 mm, the temperature TI at the central area isabout 50° C., and the temperature TO at the outer peripheral area isabout 40° C.

That is, the present inventors have found that it is desirable to usethe method of adjusting the gap G and the method of adjusting thetemperature distribution of the wafer together in order to independentlycontrol the distribution of ion flux and the distribution of reactionamount of the radicals with low cost and high effect.

The line width CD of the line formed by an etching process may varydepending on a gap of adjacent lines (pattern gap) in addition to theadhesion coefficient.

Therefore, the line width CD of the line formed on the wafer may varydepending on the temperature of the wafer and the pattern gap.

However, as described above, if there are areas having different patterngaps in the surface of the wafer, it is difficult to independentlycontrol a line width CD of a line in the dense area A1 and a line widthCD of a line in the sparse area A2 by adjusting only the temperature ofthe wafer. In this case, it may be possible to independently control theline widths CD of the lines in the dense area A1 and the sparse area A2by adjusting the supply amount or composition ratio of the processinggas.

Further, Table 1 shows the deviation CD2σ of the line widths in thesparse area A2. As described above, the ratio between the flow rate FLIof the processing gas at the central area and the flow rate FLO of theprocessing gas at the outer peripheral area is optimized in advance to50:50. For this reason, by adjusting the gap G, the temperature TI atthe central area, and the temperature TO at the outer peripheral area,the deviation CD2σ in the sparse area A2 can be decreased to about 2.9nm under the condition that the gap G is about 50 mm, the temperature TIat the central area is about 50° C., and the temperature TO at the outerperipheral is about 40° C.

Hereinafter, referring to FIGS. 9A to 10D, there will be explained anexample where distributions of line widths CD and heights H of lines inthe surface of the wafer can be controlled independently.

FIGS. 9A to 9D are graphs schematically showing temperature dependencyof line widths CD of the line groups and gap dependency of etching ratesER in a longitudinal direction during the second mask film etchingprocess. In each of FIGS. 9A to 9D, the temperature dependency of linewidths CD in the dense area A1, the temperature dependency of linewidths CD in the sparse area A2 and the gap dependency of the etchingrates ER in the longitudinal direction are shown in sequence from theleft.

FIGS. 10A to 10D are graphs schematically showing temperature dependencyof line widths CD of the line groups and gap dependency of etching ratesER in a longitudinal direction during the first mask film etchingprocess. In each of FIGS. 10A to 10D, the temperature dependency of linewidths CD in the dense area A1, the temperature dependency of linewidths CD in the sparse area A2 and the gap dependency of the etchingrates ER in the longitudinal direction are shown in sequence from theleft.

Referring to FIGS. 10A to 10D, there will be explained an example wherein the first mask film etching process (step S14), it is possible toindependently control the distribution of line widths CD and heights Hof the line groups in the surface of the wafer and possible to performan etching process with high uniformity in cross sectional shapes of theline groups.

FIG. 10A shows each dependency before a temperature distribution, adistribution of a supply amount, and a gap G are adjusted. In FIG. 10A,a flow rate FLI at the central area is set to be FLI0 and a flow rateFLO at the outer peripheral area is set to be FLO0. FIG. 10A shows anexample where line widths CD both in the dense area A1 and in the sparsearea A2 have different temperature dependency at the central area andthe outer peripheral area of the wafer. Further, in the example shown inFIG. 10A, the temperature dependency of the line widths CD in the densearea A1 has a tendency opposite to a tendency of the temperaturedependency of the line widths CD in the sparse area A2. Furthermore, inthe example shown in FIG. 10A, etching rates ER in the longitudinaldirection have different gap dependency at the central area and theouter peripheral area of the wafer. Here, the gap G is set to be G0where a difference between the etching rates ER in the longitudinaldirection at the central area and the outer peripheral area is small.

In the example shown in FIG. 10A, when the temperature TI at the centralarea of the wafer and the temperature TO at the outer peripheral area ofthe wafer are set to be same as a temperature T0, a line width CDI1 atthe central area in the dense area A1 cannot be the same as a line widthCDO1 at the outer peripheral area in the dense area A1. Further, a linewidth CDI12 at the central area in the sparse area A2 cannot be the sameas a line width CDO2 at the outer peripheral area in the sparse area A2.

FIG. 10B shows each dependency after the temperature distribution isadjusted. As depicted in FIG. 10B, the temperature TI at the centralarea is set to be T1 lower than TO, and the temperature TO at the outerperipheral area is set to be T2 higher than T0. In this way, byadjusting the temperature distribution in the surface of the wafer, adifference between the line width CDI1 at the central area in the densearea A1 and the line width CDO1 at the outer peripheral area in thedense area A1 can be further reduced. However, since the temperaturedependency of the line widths CD in the dense area A1 has a tendencyopposite to a tendency of the temperature dependency of the line widthsCD in the sparse area A2, a difference between the line width CDI2 atthe central area in the sparse area A2 and the line width CDO2 at theouter peripheral area in the sparse area A2 may not be reduced.

FIG. 10C shows each dependency after the distribution of the supplyamount of the processing gas is adjusted. As depicted in FIG. 10C, theflow rate at the central area is set to be FLI1 lower than FLI0 and theflow rate at the outer peripheral area is set to be FLO1 higher thanFLO0. In this way, by adjusting the distribution of the gas supplyamount in the surface of the wafer, the reaction amount of the radicalsat the central area is decreased in the dense area A1 and in the sparsearea A2, and, thus, a straight line that represents the temperaturedependency of the line width CD moves downward. Meanwhile, the reactionamount of the radicals at the outer peripheral area is increased, and,thus, a straight line that represents the temperature dependency of theline width CD moves upward.

Further, the lines 13 b in the sparse area A2 are more likely to be incontact and react with the radicals than the lines 13 a in the densearea A1. For this reason, when the gas supply amount is changed, theline widths CD of the lines 13 b in the sparse area A2 may be greatlychanged as compared to the line widths CD of the lines 13 a in the densearea A1. That is, the gas supply amount dependency of the reactionamount between the lines 13 a in the dense area A1 and the radicals maybe less than the gas supply amount dependency of the reaction amountbetween the lines 13 b in the sparse area A2 and the radicals.

Therefore, by adjusting the distribution of the gas supply amount, theline widths CD can be greatly changed in the sparse area A2 as comparedto those in the dense area A1. Further, as depicted in FIG. 10C, theline width CDI1 at the central area in the dense area A1 may be set tobe substantially the same as the line width CDO1 at the outer peripheralarea in the dense area A1, and the line width CDI12 at the central areain the sparse area A2 may be set to be substantially the same as theline width CDO2 at the outer peripheral area in the sparse area A2.

However, if the gas supply amount is changed, an ion flux may bechanged. Thus, as depicted in FIG. 10C, an etching rate ER in thelongitudinal direction may be also changed. The ion flux at the centralarea is decreased and the ion flux at the outer peripheral area isincreased. Thus, when the gap is G0, a difference between an etchingrate ERI in the longitudinal direction at the central area and anetching rate ERO in the longitudinal direction at the outer peripheralarea becomes increased as compared to a difference in the case beforethe temperature distribution and the gas supply amount in the wafersurface are adjusted.

In the first mask film etching process (step S14), by adjusting the gapG, the difference between the etching rate ERI in the longitudinaldirection at the central area and the etching rate ERO in thelongitudinal direction at the outer peripheral area may be decreased.

FIG. 10D shows each dependency after the gap G is adjusted. In theexample shown in FIG. 10D, the gap is set to be G1 smaller than G0.Thus, the difference between the etching rate ERI in the longitudinaldirection at the central area and the etching rate ERO in thelongitudinal direction at the outer peripheral area can be decreased.Therefore, after the distribution of the reaction amount of the radicalsin the wafer surface is adjusted, the etching rate ER in thelongitudinal direction in the wafer surface may be adjusted.

As described above, in the first mask film etching process (step S14),by adjusting the gap G in addition to controlling the temperaturedistribution and the supply amount or composition ratio of theprocessing gas, it is possible to independently control the distributionof line widths CD of the line groups and the distribution of etchingrates ER in the longitudinal direction. Consequently, the line widths CDand the heights H in the surface of the wafer can be uniformed and crosssections of the line groups may also be uniformed.

Hereinafter, there will be explained an example where it is possible toindependently control the distribution of line widths CD and heights Hof line groups in a surface of a wafer and to perform an etching processwith high uniformity in cross sectional shapes of lines in the secondmask film etching process (step S13) shown in FIGS. 9A to 9D.

FIG. 9A shows each dependency before a temperature distribution, adistribution of a supply amount, and a gap G are adjusted. In FIG. 9A, aflow rate FLI at a central area is set to be FLI0 and a flow rate FLO atan outer peripheral area is set to be FLO0. FIG. 9A shows an examplewhere line widths CD both in a dense area A1 and in a sparse area A2have little temperature dependency at the central area and the outerperipheral area of the wafer. Further, in the example shown in FIG. 9A,etching rates ER in the longitudinal direction have different gapdependency at the central area and the outer peripheral area of thewafer. Here, the gap G is set to be G0 where a difference between theetching rates ER in the longitudinal direction at the central area andthe outer peripheral area is small.

That is, temperature dependency of a reaction amount between radicalsand the surface of the second mask film 14 in the second mask filmetching process (step S13) may be smaller than temperature dependency ofa reaction amount between radicals and the surface of the first maskfilm 13 in the first mask film etching process (step S14). The radicalsin the second mask film etching process (step S13) serve as firstneutral particles of the present disclosure. Further, the radicals inthe first mask film etching process (step S14) serve as second neutralparticles of the present disclosure.

In the example shown in FIG. 9A, when a temperature TI at the centralarea of the wafer and a temperature TO at the outer peripheral area ofthe wafer are set to be same as a temperature T0, a line width CDI1 atthe central area in the dense area A1 cannot be the same as a line widthCDO1 at the outer peripheral area in the dense area A1. Further, a linewidth CD12 at the central area in the sparse area A2 cannot be the sameas a line width CDO2 at the outer peripheral area in the sparse area A2.

The line widths CD have little temperature dependency when theprocessing gas has a small reaction rate between radicals and sidewallsof lines or the radicals adhering to the sidewalls of the lines has alow adhesion coefficient. As described above, in the second mask filmetching process (step S13), an oxygen (O₂) gas is used as the processinggas, but oxygen radicals (O*) contained in plasma may have a lowreaction coefficient and a low adhesion coefficient.

FIG. 9B shows each dependency after the temperature dependency ischanged. As depicted in FIG. 9B, originally, the line widths CD havelittle temperature dependency both in the dense area A1 and the sparsearea A2. Therefore, even if the temperature TI at the central area isset to be T1 lower than T0 and the temperature TO at the outerperipheral area is set to be T2 higher than T0, a difference between theline width CDI1 at the central area in the dense area A1 and the linewidth CDO1 at the outer peripheral area in the dense area A1 may not bedecreased. Further, a difference between the line width CDI2 at thecentral area in the sparse area A2 and the line width CDO2 at the outerperipheral area in the sparse area A2 may not be decreased.

FIG. 9C shows each dependency after the distribution of the supplyamount of the processing gas is adjusted. As depicted in FIG. 9C, theflow rate at the central area is set to be FLI1 lower than FLI0 and theflow rate at the outer peripheral area is set to be FLO1 higher thanFLO0. In this way, by adjusting the distribution of the gas supplyamount in the surface of the wafer, the reaction amount of the radicalsat the central area is decreased in the dense area A1 and in the sparsearea A2, and, thus, a straight line that represents the temperaturedependency of the line width CD moves downward. Meanwhile, the reactionamount of the radicals at the outer peripheral area is increased, and,thus, a straight line that represents the temperature dependency of theline width CD moves upward.

In the same manner as the first mask film, etching process (step S14),by way of example, the lines 14 b in the sparse area A2 are more likelyto be in contact and react with the radicals than the lines 14 a in thedense area A1. For this reason, when the gas supply amount is changed,the line widths CD of the lines 14 b in the sparse area A2 may begreatly changed as compared to the line widths CD of the lines 14 a inthe dense area A1. That is, the gas supply amount dependency of thereaction amount between the lines 14 a in the dense area A1 and theradicals may be less than the gas supply amount dependency of thereaction amount between the lines 14 b in the sparse area A2 and theradicals.

Therefore, by adjusting the distribution of the gas supply amount, theline widths CD can be greatly changed in the sparse area A2 as comparedto those in the dense area A1. Further, as depicted in FIG. 9C, the linewidth CDI1 at the central area in the dense area A1 may be set to besubstantially the same as the line width CDO1 at the outer peripheralarea in the dense area A1, and the line width CDI12 at the central areain the sparse area A2 may be set to be substantially the same as theline width CDO2 at the outer peripheral area in the sparse area A2.

However, in the same manner as the example shown in FIGS. 10A to 10D, ifthe gas supply amount is changed, an ion flux as well as the supplyamount of the radicals may be changed. Thus, as depicted in FIG. 9C, anetching rate ER in the longitudinal direction may be changed. The ionflux at the central area is decreased and the ion flux at the outerperipheral area is increased. Thus, when the gap is G0, a differencebetween an etching rate ERI in the longitudinal direction at the centralarea and an etching rate ERO in the longitudinal direction at the outerperipheral area becomes increased as compared to a difference in thecase before the temperature distribution and the gas supply amount inthe wafer surface are adjusted.

In the second mask film etching process (step S13), by adjusting the gapG, the difference between the etching rate ERI in the longitudinaldirection at the central area and the etching rate ERO in thelongitudinal direction at the outer peripheral area may be decreased.

FIG. 9D shows each dependency after the gap G is adjusted. In theexample shown in FIG. 9D, the gap is set to be G1 smaller than G0. Thus,the difference between the etching rate ERI in the longitudinaldirection at the central area and the etching rate ERO in thelongitudinal direction at the outer peripheral area can be decreased.Therefore, after the distribution of the reaction amount of the radicalsin the wafer surface is adjusted, the etching rate ER in thelongitudinal direction in the wafer surface may be adjusted.

As described above, in the second mask film etching process (step S13),the processing gas having a low reaction rate or adhesion coefficient ofthe radicals is used, and, thus, even if the temperature of the waferand the supply amount or composition ratio of the processing gas areadjusted, it is impossible to control the line widths CD of the lines.However, by adjusting the gap G in addition to controlling thetemperature distribution and the supply amount or composition ratio ofthe processing gas, it is possible to independently control thedistribution of line widths CD of the line groups and the distributionof etching rates ER in the longitudinal direction. Consequently, theline widths CD and the heights H in the surface of the wafer can beuniformed and uniform cross sectional shape can be achieved.

In the example described with reference to FIGS. 9A to 10D, for thesimplicity of explanation, it has been explained that the temperaturedistribution in the wafer surface is first adjusted; the distribution ofthe gas supply amount in the wafer surface is then adjusted; and thenthe gap G is finally adjusted. However, the sequence of adjusting thetemperature distribution, the distribution of gas supply amounts, andthe gap G is not limited thereto, and their adjustments can be carriedout in any sequence.

Further, it may be possible to prepare in advance data of line widths CDand etching rates ER in a longitudinal direction in the dense area A1and the sparse area A2, which are obtained under respective conditionsof the temperatures TI and TO at the central area and the outerperipheral area, the flow rates FLI and FLO at the central area and theouter peripheral area, and the gap G. In this case, each condition maybe optimized such that the distributions of line widths CD and etchingrates ER in the wafer surface can be uniformed based on the dataprepared in advance. The optimization of each condition can be carriedout by the apparatus controller 190.

Further, when selecting a mask film and a processing gas for etching themask film, it is desirable to control a distribution of shapes of linesin the wafer surface while achieving selectivity in etching ratesbetween an upper film and a lower film when the mask film is etched.Therefore, in accordance with the present embodiment, it may be possibleto use a mask film including inorganic and organic films capable ofincreasing selectivity in etching rates for each processing gas when theprocessing gas is varied. Thus, it may be possible to transfer a shapeof a resist pattern onto an etching target film with high accuracy andalso possible to uniform a distribution of shapes of lines formed of theetching target film in the wafer surface.

The present embodiment has been explained for the example where the maskfilm is composed of the upper mask film including the organic film andthe lower mask film including the inorganic film. However, the presentembodiment can also be applied to a case where a mask film includes onlya single film and in this case, it is also possible to uniform adistribution of shapes of lines formed of an etching target film in awafer surface.

Modification Example of First Embodiment

Hereinafter, a plasma etching method and a plasma etching apparatus inaccordance with a modification example of the first embodiment will beexplained.

The present modification example is different from the first embodimentin that when an organic film is etched, a processing gas having a highadhesion coefficient and having radicals of a high reaction rate is usedin a second mask film etching process.

In the present modification example, the plasma etching apparatusexplained with reference to FIGS. 1 to 5 may be used, as in the firstembodiment. Further, as the first embodiment, a plasma etching method inaccordance with the present modification example also includes a resistpattern forming process (step S11), an anti-reflective coating etchingprocess (step S12), a second mask film etching process (step S13), afirst mask film etching process (step S14), and an etching target filmetching process (step S15) explained with reference to FIG. 6.Furthermore, a wafer state in each process is the same as illustrated inFIGS. 7A to 7E.

Meanwhile, in the present modification example, in the second mask filmetching process (step S13), it may be possible to use a mixed gasincluding a nitrogen (N₂) gas/a hydrogen (H₂) gas instead of an oxygen(O₂) gas as a processing gas. When a temperature distribution, adistribution of a supply amount, and a gap G are adjusted in the secondmask film etching process (step S13), example processing conditionsother than the processing gas are as follows.

(C) Second Mask Film Etching Process (Step S13)

Material of second mask film: naphthalene (or polystyrene)

Thickness of second mask film: 280 nm

Internal pressure of film forming apparatus: 100 mTorr

High frequency power (40 mHz/13 MHz): 700/0 W

Potential of upper electrode: 0 V

Flow rate of processing gas: N₂/H₂=160/480 sccm

Processing time: 60 seconds

When the second mask film 14 is etched by using the mixed gas includingthe nitrogen (N₂) gas/the hydrogen (H₂) gas, line widths CD may beobserved to have temperature dependency and gas supply amount dependencyand an etching rate ER in a longitudinal direction may have gapdependency in the same way as described in the first embodiment in FIGS.10A to 10D. Therefore, the temperature distribution, the distribution ofthe supply amount, and the gap G can be adjusted in the same manner asthe first mask film etching process (step S14) in the first embodiment.

That is, as depicted in FIG. 10A, a line width CD has differenttemperature dependency at a central area and an outer peripheral area ofa wafer. For this reason, as depicted in FIG. 10B, by adjusting only thetemperature distribution in the wafer surface, it is possible todecrease a difference between a line width CDI1 at the central area in adense area A1 and a line width CDO1 at the outer peripheral area in thedense area A1 but it is impossible to decrease a difference between aline width CDI2 at the central area in a sparse area A2 and a line widthCDO2 at the outer peripheral area in the sparse area A2. Further, asdepicted in FIG. 100, by adjusting flow rates FLI and FLO of theprocessing gas at the central area and the outer peripheral area, it ispossible to make the line width CDI1 at the central area in the densearea A1 substantially the same as the line width CDO1 at the outerperipheral area in the dense area A1 and also possible to make the linewidth CDI2 at the central area in the sparse area A2 substantially thesame as the line width CDO2 at the outer peripheral area in the sparsearea A2. Here, since the ion flux is also changed, by adjusting the gapG, it is possible to decrease a difference between the etching rate ERIin the longitudinal direction at the central area and the etching rateERO in the longitudinal direction at the outer peripheral area asdepicted in FIG. 10D.

Therefore, in accordance with the present embodiment, it may be possibleto use a mask film including inorganic and organic films capable ofincreasing selectivity in etching rates for each processing gas when theprocessing gas is varied. Thus, it may be possible to transfer a shapeof a resist pattern onto an etching target film with high accuracy andalso possible to uniform a distribution of shapes of lines formed of theetching target film in the wafer surface.

Further, the present modification example can also be applied to a casewhere a mask film is composed of a film including either an organic filmor an inorganic film and in such a case, it is possible to uniform adistribution of shapes of lines formed of an etching target film in awafer surface.

Second Embodiment

Hereinafter, referring to FIGS. 11 to 15, a plasma etching method and aplasma etching apparatus in accordance with a second embodiment of thepresent disclosure will be explained.

The present embodiment is different from the first embodiment in that adistribution of a gas supply amount in a wafer surface is not adjustedand a pattern to be formed does not have a sparse area but only has adense area.

Referring to FIGS. 11 to 15, the plasma etching apparatus in accordancewith the present embodiment will be elaborated. FIGS. 11 and 12 arecross sectional views showing a schematic configuration of the plasmaetching apparatus in accordance with the present embodiment. To bespecific, FIG. 11 shows a configuration in which an upper electrode islocated at a retreat position, and FIG. 12 shows a configuration inwhich the upper electrode is located at a process position. FIGS. 13 aand 13 b provide explanatory diagrams simply showing an upper electrodedriving unit. To be specific, FIG. 13A shows a configuration in whichthe upper electrode is located at the retreat position and FIG. 13Bshows a configuration in which the upper electrode is located at theprocess position.

As depicted in FIGS. 11 to 13B, a plasma etching apparatus 100 a has thesame components as those of the plasma etching apparatus 100 explainedwith reference to FIGS. 1 to 3B except for a shower head 140 a (upperelectrode 120 a) and a gas supply apparatus 150 a, and the samecomponents are assigned with same reference numerals as those of theplasma etching apparatus 100 and explanation thereof will be omitted.

The shower head 140 a is configured to supply a mixed gas onto the waferW supported on a susceptor 105. The shower head 140 a includes acircular electrode plate 141 (upper electrode 120 a) having a multiplenumber of gas discharge holes 141 a and an electrode support body 142which supports the surface of the electrode plate 141 and is detachabletherefrom as explained in the first embodiment. Further, the electrodesupport 142 and a buffer room 143 c are configured in the same manner asthe first embodiment.

Meanwhile, in the present embodiment, an annular partition wall member145 formed of an O-ring is not installed in the buffer room 143 c andthe buffer room is not divided into plural sections. A bottom surface ofthe buffer room 140 c communicates with gas discharge holes 141 a, andthe mixed gas can be discharged toward the wafer W. Further, the mixedgas is supplied to the buffer room 143 c by a gas supply apparatus 150a.

As depicted in FIGS. 13A and 13B, a detail configuration of the upperelectrode driving unit 200 is the same as explained in the firstembodiment. However, in the present embodiment, as described below, amixing line 170 for supplying a gas into the buffer room 143 c of theupper electrode 120 a is not divided and is configured as a single line.For this reason, a diameter of the bellows 122 may be smaller ascompared to that in the first embodiment.

Hereinafter, referring to FIGS. 11, 12, 14 and 15, the gas supplyapparatus 150 a will be explained. FIG. 14 is transversal crosssectional view of an upper electrode. FIG. 15 is a diagram forexplaining a schematic configuration of a gas supply apparatus.

The gas supply apparatus 150 a includes a gas box 161 which accommodatesa multiple number of, for example, three, gas supply sources 160 a, 160b, and 160 c. By way of example, a C_(X)F_(Y) gas such as CF₄, C₄F₆,C₄F₈, and C₅F₈ is sealed in a gas supply source 160 a, an oxygen (O₂)gas is sealed in a gas supply source 160 b, and an Ar gas is sealed in agas supply source 160 c.

Each of the gas supply sources 160 a to 160 c is connected with themixing line 170 via a mass flow controller 171. Further, the mixing line170 is not divided and is connected with the buffer room 143 c of theshower head 140 a.

A pressure adjusting unit 174 is installed on a part of the mixing line170, and the pressure adjusting unit 174 includes a pressure gauge 174 aand a valve 174 b. A measurement result measured by the pressure gauge174 a of the pressure adjusting unit 174 may be outputted by a pressurecontrol apparatus 176. The pressure control apparatus 176 adjusts anopening/closing degree of the valve 174 b based on the measurementresult of the pressure gauge 174 a and controls a flow rate of theprocessing gas flowing through the mixing line 170.

An operation of the mass flow controller 171 of the gas box 161 iscontrolled by, for example, an apparatus controller 190 of the plasmaetching apparatus 100 a. Therefore, the apparatus controller 190 maycontrol a start and a stop of supply of various gases from the gas box161 and control a supply amount of the various gases.

Hereinafter, referring to FIGS. 16 to 17E, a plasma etching method usingthe plasma etching apparatus 100 a will be explained. FIG. 16 is aflowchart for explaining a process sequence of a plasma etching methodin accordance with the present embodiment. FIGS. 17A to 17E are crosssectional views schematically showing wafer states in each process ofthe plasma etching method in accordance with the present embodiment.

The plasma etching method in accordance with the present embodiment, asdepicted in FIG. 16, includes a resist pattern forming process (stepS21), an anti-reflective coating etching process (step S22), a secondmask film etching process (step S23), a first mask film etching process(step S24), and an etching target film etching process (step S25).

First, the resist pattern forming process (step S21) is performed. Theresist pattern forming process (step S21) may be performed in the samemanner as the resist pattern forming process (step S11) of the firstembodiment. FIG. 17A shows a wafer state in the resist pattern formingprocess (step S21). However, as depicted in FIG. 17 a, in the presentembodiment, only an area (dense area) A1 in which lines 16 a arearranged at a distance D1 is formed and a sparse area is not formed.

Then, the anti-reflective coating etching process (step S22) isperformed. The anti-reflective coating etching process (step S22) may beperformed in the same manner as the anti-reflective coating etchingprocess (step S12) of the first embodiment. FIG. 17B shows a wafer statein the anti-reflective coating etching process (step S22).

Subsequently, the second mask film etching process (step S23) isperformed. In the second mask film etching process (step S23), a secondmask film 14 is etched by plasma irradiated to a wafer 10 using lines 15a formed of a resist film 16 and an anti-reflective coating 15, so thatlines 14 a including the second mask film 14 are formed. FIG. 17C showsa wafer state in the second mask film etching process (step S23).

In the second mask film etching process (step S23), a temperaturedistribution in the surface of the wafer 10 supported on the susceptor105 is adjusted. By this adjustment, a distribution of reaction amountsbetween the radicals of the plasma in the surface of the wafer 10 andthe surface of the wafer 10 is controlled. By controlling thedistribution of the reaction amounts, it is possible to control adistribution of line widths CD of the lines 14 a in the surface of thewafer 10.

In response to a control signal from an apparatus controller 190 to atemperature distribution adjusting unit 106, temperatures of central andouter peripheral thermometers 106 e and 106 f are adjusted topredetermined temperatures TI and TO, respectively. Further, in responseto a control signal from the apparatus controller 190 to the temperaturedistribution adjusting unit 106, a central heater 106 a and an outerperipheral heater 106 b are controlled independently. Consequently, itis possible to set the temperature TI at the central area of the wafer10 to be different from the temperature TO at the outer peripheral areaof the wafer 10, and, thus, a temperature distribution in the surface ofthe wafer 10 can be adjusted.

As described above, by adjusting the temperature distribution in thesurface of the wafer 10, it is possible to control the distribution ofthe line widths CD of the lines 14 a formed of the second mask film 14in the surface of the wafer 10.

In the second mask film etching process (step S23), in response to acontrol signal from the apparatus controller 190 to an upper electrodedriving unit 200, a gap G between the wafer 10 supported on thesusceptor 105 and the upper electrode 120 a provided so as to face thewafer 10 is adjusted. By adjusting the gap G, it is possible to controla distribution of irradiation amounts of ions in the surface of thewafer 10 and a distribution of etching rates ER in a longitudinaldirection (depth direction). Further, by controlling the distribution ofthe etching rates ER in the longitudinal direction (depth direction), itis possible to control a distribution of heights H of the lines 14 a inthe surface of the wafer 10.

In the second mask film etching process (step S23), it may be possibleto use an oxygen (O₂) gas as the processing gas.

Thereafter, the first mask film etching process (step S24) is performed.In the first mask film etching process (step S24), the first mask film13 is etched by plasma irradiated to the wafer 10 using the lines 14 aformed of the second mask film 14 as a mask, so that lines 13 aincluding the first mask film 13 are formed. FIG. 17D shows a waferstate in the first mask film etching process (step S24).

In the first mask film etching process (step S24), a temperaturedistribution in the surface of the wafer 10 supported on the susceptor105 is adjusted. By this adjustment, the distribution of the reactionamounts between the radicals of the plasma in the surface of the wafer10 and the surface of the wafer 10 is controlled. By controlling thedistribution of the reaction amounts, it is possible to control adistribution of the line widths CD of the lines 13 a in the surface ofthe wafer 10.

Further, in the first mask film etching process (step S24), in responseto a control signal from the apparatus controller 190 to the upperelectrode driving unit 200, a gap G between the wafer 10 supported onthe susceptor 105 and the upper electrode 120 a provided so as to facethe wafer 10 is adjusted. By adjusting the gap G, it is possible tocontrol a distribution of irradiation amounts of ions in the surface ofthe wafer 10 and a distribution of etching rates ER in a longitudinaldirection (depth direction). Further, by controlling the distribution ofthe etching rates ER in the longitudinal direction (depth direction), itis possible to control a distribution of heights H of the lines 13 a inthe surface of the wafer 10.

In the first mask film etching process (step S24), as the processinggas, it may be possible to use a mixed gas of a CF-based gas such asCF₄, C₄F₈, CHF₃, CH₃F, and CH₂F₂ with an Ar gas, or the mixed gasfurther including an oxygen (O₂) gas if necessary.

Thereafter, the etching target film etching process (step S25) isperformed in the same manner as the etching target film etching process(step S15) of the first embodiment. FIG. 17E shows a status of a waferin the etching target film etching process (step S25).

Hereinafter, there will be explained a case where a distribution of linewidths CD of lines and a distribution of heights H of the lines in asurface of a wafer are independently controlled and an etching processcan be performed with high uniformity in cross sectional shapes of lineswhen the etching process is performed on the wafer using the plasmaetching method in accordance with the present embodiment.

In the present embodiment, it is possible to independently control adistribution of ion fluxes and a distribution of reaction amounts ofradicals by using a method of controlling the distribution of ion fluxesby adjusting a gap G and a method of controlling the distribution of thereaction amounts of the radicals by adjusting a temperature distributionin a wafer.

Herein, referring to FIGS. 18A to 18C, there will be explained anexample where distributions of line widths CD of lines and thedistribution of heights H of lines in the surface of the wafer can beindependently controlled.

FIGS. 18A to 18C are graphs schematically showing temperature dependencyof line widths CD of lines and gap dependency of etching rates ER in alongitudinal direction in the present embodiment. In each of FIGS. 18Ato 18C, the temperature dependency of line widths CD and the gapdependency of the etching rates ER in the longitudinal direction areshown in sequence from the left.

Further, when a temperature distribution, a distribution of a supplyamount, and a gap G are adjusted in the second mask film etching process(step S23) and the first mask film etching process (step S24), exampleprocessing conditions other than the processing gas are as follows.

(D) Second Mask Film Etching Process (Step S23)

Material of second mask film: naphthalene (or polystyrene)

Thickness of second mask film: 280 nm

Internal pressure of film forming apparatus: 100 mTorr

High frequency power (40 mHz/13 MHz): 700/0 W

Potential of upper electrode: 0 V

Flow rate of processing gas: N₂/H₂=160/480 sccm

Processing time: 60 seconds

(E) First Mask Film Etching Process (Step S24)

Material of first mask film: TEOS-SiO₂

Thickness of first mask film: 280 nm

Internal pressure of film forming apparatus: 75 mTorr

High frequency power (40 mHz/13 MHz): 500/0 W

Potential of upper electrode: 300 V

Flow rate of processing gas: CHF₃/CF₄/Ar/O₂=125/225/600/60 sccm (here,CH₂F₂ of 20 sccm may be added to outer peripheral area)

Processing time: 60 seconds

In the present embodiment, when the organic film is etched, a processinggas having a high adhesion coefficient and having radicals of a highreaction rate is used as in the modification example of the firstembodiment. Therefore, the second mask film etching process (step S23)and the first mask film etching process (step S24) can be explained withreference to FIGS. 18A to 18C.

FIG. 18A shows each dependency before a temperature distribution and agap G are adjusted. FIG. 18A shows an example where line widths CD havedifferent temperature dependency at the central area of the wafer andthe outer peripheral area of the wafer. Further, in the example shown inFIG. 18A, the etching rates ER in the longitudinal direction havedifferent gap dependency at the central area of the wafer and the outerperipheral area of the wafer.

FIG. 18B shows each dependency after the temperature distribution isadjusted. As depicted in FIG. 18B, the temperature TI at the centralarea is set to be T1 lower than T0 and the temperature TO at the outerperipheral area is set to be T2 higher than T0. In this way, byadjusting the temperature distribution in the surface of the wafer, adifference between the line width CDI at the central area and the linewidth CDO at the outer peripheral area can be further reduced.

FIG. 18C shows each dependency after the gap G is adjusted. In theexample shown in FIG. 18C, the gap is set to be G1 greater than G0.Thus, a difference between the etching rate ERI in the longitudinaldirection at the central area and the etching rate ERO in thelongitudinal direction at the outer peripheral area can be furtherreduced. Therefore, after the distribution of the reaction amount of theradicals in the wafer surface is adjusted, the etching rate ER in thelongitudinal direction in the wafer surface may be adjusted.

In the present embodiment, it may be possible to use a mask filmincluding inorganic and organic films capable of increasing selectivityin etching rates for each processing gas when the processing gas isvaried. Thus, it may be possible to transfer a shape of a resist patternonto an etching target film with high accuracy and also possible touniform a distribution of shapes of lines formed of the etching targetfilm in the wafer surface.

Further, the present embodiment can be applied to a case where a maskfilm includes only a single film and in this case, it is also possibleto uniform a distribution of shapes of lines formed of an etching targetfilm in a wafer surface.

As described above, there have been explained embodiments of the presentdisclosure, but the present invention is not limited to theabove-described embodiments and can be modified and changed in variousways within a scope of the following claims.

1. A plasma etching method for performing a plasma etching on asubstrate by irradiating plasma containing charged particles and neutralparticles to the substrate, the method comprising: controlling adistribution of reaction amounts between the substrate and the neutralparticles in a surface of the substrate by adjusting a temperaturedistribution in the surface of the substrate supported by a support; andcontrolling a distribution of irradiation amounts of the chargedparticles in the surface of the substrate by adjusting a gap between thesubstrate supported by the support and an electrode provided so as toface the support.
 2. The plasma etching method of claim 1, furthercomprising: an etching process for forming lines including a mask filmby etching the mask film formed on the substrate by the irradiatedplasma, wherein, in the etching process, a distribution of line widthsof the lines in the surface of the substrate is controlled by adjustingthe distribution of reaction amounts, and a distribution of heights ofthe lines in the surface of the substrate is controlled by adjusting thedistribution of irradiation amounts.
 3. The plasma etching method ofclaim 2, wherein the etching process includes: a second mask filmetching process for forming the lines including a second mask film byirradiating first plasma containing first charged particles and firstneutral particles to the substrate and etching the second mask filmformed on the substrate via a first mask film by the irradiated firstplasma; and a first mask film etching process for forming the linesincluding the first mask film by irradiating second plasma containingsecond charged particles and second neutral particles to the substrateon which the lines including the second mask film are formed and etchingthe first mask film by the irradiated second plasma, wherein temperaturedependency of a reaction amount between the second mask film and thefirst neutral particles is lower than temperature dependency of areaction amount between the first mask film and the second neutralparticles.
 4. The plasma etching method of claim 1, wherein thedistribution of reaction amounts in the surface of the substrate iscontrolled by adjusting the temperature distribution and a distributionof a supply amount or a composition ratio of a processing gas suppliedto the substrate.
 5. The plasma etching method of claim 4, furthercomprising: an etching process for forming first lines including themask film and spaced apart from each other at a first gap and secondlines including the mask film and spaced apart from each other at asecond gap greater than the first gap by etching the mask film formed onthe substrate by the irradiated plasma, wherein, in the etching process,a distribution of line widths of the first lines and the second lines inthe surface of the substrate is controlled by adjusting the distributionof reaction amounts, and a distribution of heights of the first linesand the second lines in the surface of the substrate is controlled byadjusting the distribution of irradiation amounts, and temperaturedependency of a first reaction amount between the first lines and theneutral particles is lower than temperature dependency of a secondreaction amount between the second lines and the neutral particles. 6.The plasma etching method of claim 5, wherein the etching processincludes: a second mask film etching process for forming the first linesand the second lines each including a second mask film by irradiatingfirst plasma containing first charged particles and first neutralparticles to the substrate and etching the second mask film formed onthe substrate via a first mask film by the irradiated first plasma; anda first mask film etching process for forming the first lines and thesecond lines each including the first mask film by irradiating secondplasma containing second charged particles and second neutral particlesto the substrate on which the first lines and the second lines eachincluding the second mask film are formed and etching the first maskfilm by the irradiated second plasma, wherein temperature dependency ofa reaction amount between the second mask film and the first neutralparticles is lower than temperature dependency of a reaction amountbetween the first mask film and the second neutral particles.
 7. Theplasma etching method of claim 3, wherein the first mask film includesan inorganic film and the second mask film includes an organic film, andthe first neutral particles include oxygen radicals and the secondneutral particles include fluorine radicals.
 8. The plasma etchingmethod of claim 6, wherein the first mask film includes an inorganicfilm and the second mask film includes an organic film, and the firstneutral particles include oxygen radicals and the second neutralparticles include fluorine radicals.
 9. A plasma etching apparatusconfigured to perform a plasma etching on a substrate by irradiatingplasma containing charged particles and neutral particles to thesubstrate, the apparatus comprising: a support capable of supporting thesubstrate; an electrode provided so as to face the support; atemperature distribution adjusting unit capable of adjusting atemperature distribution in a surface of the substrate supported by thesupport; a gap adjusting unit capable of adjusting a gap between thesubstrate supported by the support and the electrode; and a controllercapable of controlling a distribution of reaction amounts between thesubstrate and the neutral particles in the surface of the substrate byadjusting the temperature distribution by the temperature distributionadjusting unit and capable of controlling a distribution of irradiationamounts of the charged particles in the surface of the substrate byadjusting the gap by the gap adjusting unit.
 10. The plasma etchingapparatus of claim 9, wherein lines including a mask film are formed byetching the mask film formed on the substrate by the irradiated plasma,and when the lines are formed, the controller controls a distribution ofline widths of the lines in the surface of the substrate by adjustingthe distribution of reaction amounts, and the controller controls adistribution of heights of the lines in the surface of the substrate byadjusting the distribution of irradiation amounts.
 11. The plasmaetching apparatus of claim 10, wherein the lines including a second maskfilm are formed by irradiating first plasma containing first chargedparticles and first neutral particles to the substrate and etching thesecond mask film formed on the substrate via a first mask film by theirradiated first plasma; and the lines including the first mask film areformed by irradiating second plasma containing second charged particlesand second neutral particles to the substrate on which the linesincluding the second mask film are formed and etching the first maskfilm by the irradiated second plasma, wherein temperature dependency ofa reaction amount between the second mask film and the first neutralparticles is lower than temperature dependency of a reaction amountbetween the first mask film and the second neutral particles.
 12. Theplasma etching apparatus of claim 9, further comprising: a supply amountdistribution adjusting unit capable of adjusting a distribution of asupply amount or a composition ratio of a processing gas supplied to thesubstrate in the surface of the substrate, wherein the controllercontrols the distribution of reaction amounts by adjusting thetemperature distribution by the temperature distribution adjusting unitand by adjusting the distribution of the supply amount or compositionratio in the surface of the substrate by the supply amount distributionadjusting unit.
 13. The plasma etching apparatus of claim 12, whereinfirst lines spaced apart from each other at a first gap and includingthe mask film and second lines spaced apart from each other at a secondgap greater than the first gap and including the mask film are formed byetching the mask film formed on the substrate by the irradiated plasma,when the first lines and the second lines are formed, the controllercontrols a distribution of line widths of the first lines and the secondlines in the surface of the substrate by adjusting the distribution ofreaction amounts, and the controller controls a distribution of heightsof the first lines and the second lines in the surface of the substrateby adjusting the distribution of irradiation amounts, and temperaturedependency of a first reaction amount between the first lines and theneutral particles is lower than temperature dependency of a secondreaction amount between the second lines and the neutral particles. 14.The plasma etching apparatus of claim 13, wherein the first lines andthe second lines each including a second mask film are formed byirradiating first plasma containing first charged particles and firstneutral particles to the substrate and etching the second mask filmformed on the substrate via a first mask film by the irradiated firstplasma; and the first lines and the second lines each including thefirst mask film are formed by irradiating second plasma containingsecond charged particles and second neutral particles to the substrateon which the first lines and the second lines each including the secondmask film are formed and etching the first mask film by the irradiatedsecond plasma, wherein temperature dependency of a reaction amountbetween the second mask film and the first neutral particles is lowerthan temperature dependency of a reaction amount between the first maskfilm and the second neutral particles.
 15. The plasma etching apparatusof claim 11, wherein the first mask film includes an inorganic film andthe second mask film includes an organic film, and the first neutralparticles include oxygen radicals and the second neutral particlesinclude fluorine radicals.
 16. The plasma etching apparatus of claim 14,wherein the first mask film includes an inorganic film and the secondmask film includes an organic film, and the first neutral particlesinclude oxygen radicals and the second neutral particles includefluorine radicals.